Environmental Rules in Thornton, CO (2026)
4 verified environmental rules for Thornton, Colorado, sourced directly from the municipal code and official government pages.
Verified from official government sources
Stormwater Management
Thornton requires a stormwater quality permit before disturbing more than one acre of land, City Code Section 22-115. Permits run up to two years, cap disturbance at 40 acres at a time absent a director's variance, and carry fees set by city council resolution. The stormwater coordinator and development engineering manager administer the program under Chapter 22, Article V.
Thornton Stormwater Quality Permit Requirement
Some RestrictionsThornton City Code § 22-115
A stormwater quality permit will be required for any land disturbance activity of more than one acre of surface area. Additionally, land disturbance activity may be permitted to be phased so that no more than 40 acres surface area within a development is disturbed at any given time. Variances allowing for more than 40 acres of disturbance at one time may be authorized by the director. Applicati...
Erosion Control
Under City Code Section 22-156(5), anyone holding a Thornton grading or stormwater quality permit must stop sediment and dust from leaving the site using temporary and permanent best management practices, maintain those measures until the site is fully stabilized, and remove them once vegetation is established. Projects disturbing more than an acre also need a state discharge permit or sediment control plan before construction begins.
Thornton Erosion and Sediment Control Duties
Some RestrictionsThornton City Code § 22-156(5)
Erosion, sediment, and dust control. The permittee shall be responsible to prevent discharge of sediment or dust from the site to any watercourse, drainage system, or adjacent property by implementing temporary and permanent BMPs and to protect from all damage that may result from wind, erosion, or sedimentation from the site. The permittee shall be responsible for maintenance of all temporary ...
Flood Zones
Thornton requires a floodplain development permit under City Code Section 22-312 before any construction or development begins within an area of special flood hazard. The floodplain administrator reviews applications alongside standard Chapter 18 development review, requires elevation certifications and engineer sign-off, and relies on FEMA's December 2021 Flood Insurance Study and accompanying maps to define the regulated area.
Thornton Floodplain Development Permit Required
Significant RestrictionsThornton City Code § 22-312(a)
A floodplain development permit is required before construction or development begins within any area of special flood hazard established under Section 22-303. In addition, any application for any development permit on a parcel which has special flood hazard area shown on any portion of the parcel shall be evaluated to determine whether it involves the area of special flood hazard, and if so, i...
Flood Elevation Requirements
New residential construction in a Thornton special flood hazard area must set its lowest floor at least one foot above the base flood elevation, City Code Section 22-311(b)(1)a. Substantially improved or renovated homes in the flood hazard area need the same one-foot freeboard above the base flood elevation, and the elevation must be certified by a licensed Colorado engineer, architect, or surveyor.
Thornton Floodplain Freeboard Elevation Standard
Some RestrictionsThornton City Code § 22-311(b)(1)a-b
New construction and substantial improvement and/or reconstruction of any residential structure shall have the lowest floor (including basement), electrical, heating, ventilation, plumbing, and air conditioning equipment and other service facilities (including ductwork), elevated to one foot above the base flood elevation. This includes external mechanical and electrical equipment such as air c...
Looking for Adams County county-wide rules?
County ordinances apply to unincorporated areas and may supplement Thornton city rules.
Environmental Rules in Adams County →